There are two ways to specify files, by absolute file name and by block list.
An absolute file name resembles a Unix absolute file name, using
‘/’ for the directory separator (not ‘\’ as in DOS). One
example is ‘(hd0,1)/boot/grub/grub.cfg’. This means the file
/boot/grub/grub.cfg in the first partition of the first hard
disk. If you omit the device name in an absolute file name, GRUB uses
GRUB’s root device implicitly. So if you set the root device to,
say, ‘(hd1,1)’ by the command ‘set root=(hd1,1)’ (see set),
/boot/kernel is the same as
On ZFS filesystem the first path component must be volume‘@’[snapshot]. So ‘/rootvol@snap-129/boot/grub/grub.cfg’ refers to file ‘/boot/grub/grub.cfg’ in snapshot of volume ‘rootvol’ with name ‘snap-129’. Trailing ‘@’ after volume name is mandatory even if snapshot name is omitted.